Tubeless tire



May 7,1957 L. c. PETERSON ET AL. 2,791,258V

TUBELESS TIRE Filed Aug. 15, 1954 .ATTORNEY` aired Se@ 'Patent o' TUBELESS TIRE Lester C. Peterson and Harvey J. Batts, Indianapolis, Ind., assignors to United States Rubber Company, New York, N., Y., a corporation of New Jersey Application August 13, 1954, Serial No. 449,692

4 Claims. (Cl. 152-330) This invention relates to a novel air retaining element for a pneumatic rubber tire, such as an air retaining liner for a tubeless tire or an innertube for a conventional tire.

This application is a continuation-impart of our copending application Serial No. 301,432, led July 29, 1952, now abandoned. That application (Serial No. 301,432) is directed to a similar air retaining element for a pneumatic rubber tire wherein the element is formed of a continuous 'body of a vulcanized mixture comprising Butyl ru'bber reclaim and an elastomer selected from the group consisting of natural rubber and butadiene-styrene rubbery copolymer in relative proportions of from 55 to 70% of ru'bber hydrocarbon furnished by said Butyl rubber reclaim and correspondingly from 45 to 30% of said selected elastomer, said percentages being based on the sum of the weights of rubber hydrocarbon furnished by said Butyl rubber reclaim and said selected elastomer.

ln the accompanying drawing:

Fig'. 1 is a cross-sectional view of a pneumatic rubber tire of the tubeless type embodying -a liner made in accordance with our invention;

Fig. 2 is a graphical portrayal of the air retention properties of an inner tube made in accordance with' our invention and inner tubes made by prior practice; andV Fig. 3 shows in elevation a pneumatic tire inner tube embodying our invention.

Our invention is based upon the discovery that important new results and advantages are achieved by forming air retaining elements for pneumatic rubber tires, specifically liners for tubeless tires and inner tubes of conventional type,` from a vulcanized mixture of Butyl rubber reclaim and either natural rubber or butadienestyrene rubbery copolymer (GR-S). More specilically, we have found that the new results and advantages hereinafter described are achieved by forming such air retain-.

ing elements from a mixture of Butyl rubber reclaim and natural rubber or GR-S in relative proportions of from 30 to 70% of rubber hydrocarbon supplied 'by the Butyl rubber reclaim and correspondingly from 70 to 30% of natural rubber or GR-S, these percentages being by weight based on the sum of the rubber hydrocarbon supplied by the Butyl rubber reclaim and the natural rubber or GR-S.

In particular, we have found that 'by employing Butyl rubber reclaim in conjunction with natural rubber or GR-S in the foregoing proportions the air holding properties of the resulting retainer' are far superior to those of air retaining elements made entirely from natural rubber orGR-S or a mixture of both. In fact the air retention properties of Vtubelesstire liners'or inner tubes made in accordance `with our invention are almost as good as those of conventional linersor inner tubes in which the rubber is 'composedsolely'of- Butyl rubber compounded 2,791,258 Patented' `May 7, 1957 ice T tubes is extremely serious in the northern portions of theY United States and in Canada.

The second rubber component used in our invention, i. e., the natural rubber or GR-S, can consist of virgin natural rubber or GR-S, or of mixtures of reclaimed and virgin natural rubber or GR-S, or can consist entirelyk of reclaimed natural rubber or GR-S. y

In manufacturing air retaining elements in accordance with our invention we simply follow conventional factory procedures except that in place of the usual rubber formulation we employ a formulation in which the rubber component comprises Butyl rubber reclaim and natural rubber or GR-S in the relative proportions specified above.- In the preferred practice of our invention, the natural rubber or GR-S component consists of virgin natural rubber, i. e., Hevea rub-ber, or virgin GRS, respectively, although if desired a minor proportion thereof, say not over 25% thereof, can lbe replaced with an equivalent amount of natural rubber reclaim or GR-S reclaim.

The Butyl rubber reclaim land the natural rubber or GR-S are completely compatible with one another. In the practice of our invention, we typically simply mill the Butyl rubber reclaim and the natural rubber or GR-S together, adding conventional compounding ingredients, typically including suitable proportions of rubber-reinforcing carbon black, sulfur in amount sufcient to vulc-anize the resulting mixture, accelerators of vulcanization, and activators of acceleration,I especially a mixture of zinc oxide and fatty acid, e. g. stearic acid, or zinc soap, e. g., zinc stearate or zinc laurate.

The proportion of reinforcing carbon 'black employed will usually range from 20 to 60 parts per 100 parts of rubber hydrocarbon, i. e. hydrocarbon supplied by the Butyl rubber reclaim land the natural rubber or the GR-S. The proportion of sulfur may vary somewhat with variations in the proportion of natural rubber or GR-S, typically ranging from 1.0 to 2.5 parts per parts of natural rubber or GR-S. The amount of zincoxide will usually run' from 3 to 10 parts and the amount of stearic acid will generally range from 1 to 4 parts per 100 parts of natural rubber or GRS. Zinc laurate may also be used, typically in amounts ranging from 1 to 6 parts.V

An intimate mixture of the two types of rubber and the 4compounding ingredients is made in Iany suitable manner, vas on an open rubber mill or in a Banbury mixer, after which the mixture is shaped into a continuous'body having the desired linal form whereupon this body is vulcanized in any conventional manner. Details of the manufacturing method need not be given because the steps are all well known and conventional. It may Ibe stated however, that .tubeless tires embodying a liner made in accordance with our invention are customarily made by assembling them with the unvulcanized liner element ad-V t Our invention'is based upon our discovery that vul-v canized mixtures of Butyl rubber reclaim and natural rubber or GR-S in the above-mentioned proportions have physical properties which are more than adequate to meet :manette the service conditions encountered by the liner or inner tube in use, and at the same time have air retaining properties nearly as good as all-virgin Butyl rubber air retaining elements.

Referring to the drawing, Fig. 1 portrays a pneumatic tire casing 1 comprised of awmulti-ply rubberized fabric carcass Z having overlying rubber sidewall and tread prtions'3 and' 4, respectively. Inextensible beadassemblies 5 are incorporated in the lower marginal portions of the carcass. A liner elemento, formed'of a mixture of natural rubber or GR-S and Butyl reclaim in accordance with our invention, is securely attached to the entire inner portion of the carcass, preferably by vulcanization in situ while being pressed against the innermost rubberized fabric layer of the carcass during vulcanization of the tire in the factory. Preferably the outer sidewall portion of the bead is formed with a plurality of circumferential ridges 7 which arid in insuring a truly air-tight sealing against the'wheel rim. If desired, auxiliary sealant means, in addition to ridges 7, can be provided to seal the tire with Vrespect to the rim but neither ridges 7 nor such auxiliary sealant means constitute any part of ourv invention.

By reason of the complete compatibility of the stock used in the liner of our invention and the rubber stock used in the assembly of the tire carcass, an integral union of our liner with the rubber layer lover the entire inside portion of the tire carcass is effected during the vulcanization.` This effects a remarkably good adhesion of our liner to the tire'carcass and greatly simplifies the manufacture of tubeless tires having Va liner with excellent air retention properties.

` In Fig. 3 reference numeral 10 denotes an inner tube made in accordance with our invention. This inner tube is of conventional 'annular shape and need not be described in further detail. l

The following examples illustrate our invention in more detail. All parts and percentages expressed herein are by weight.

' Example 1 Liners for tubeless tires, and inner tubes, were made from the following formulation:

Parts #1 smoked sheet 40.00 Butyl rubber reclaim 1 j 2 109.00 Zinc oxide; 3.00 Stearicacid 1.00 Laurex ,j(zin,c laurate)` 2.00 Easy processing channel black 25.00 Mineral oil (viscosity 160.-l 80 Saybolt at 100 F 5.00 Benzothiazyl `disullde 0.35 Tetramethyl thiuram monosulde 0.10 Sulfur 0.75

1 Had the following analysis z SI1). gl'. 1.16 E ongation percent-- 550 Tensile p s.` i..- 1400 Acetone extract percent-- 4 Ash rln- 12 Carbon black dn 26 Rubber hydrocarbon do 55 2 60 parts rubber hydrocarbon.

These ingredients were mixed together and shaped in the ordinary way after which the liner or inner tube was formed therefrom, whereupon the tire embodying the liner, or the innerr tube, was vulcanized in the conventional manner. The resulting liners and inner tubes exhibited air holding properties almost as good las a conventional all-virgin Butyl rubber inner tube.

Examplel 2 An indication of the remarkable air retention properties of air retainers made in accordance with our invention is given by reference to Fig. 2 which is a graphical portrayal ofthe loss of airprevssure in inner tubes made in; accordance with our invention, comparedv with inner'tubes made by conventionaljpractice. The data plottedin Fig. Zwas obtained as follows: A stock was rst prepared according to the following formulation:

Parts #l smoked sheet 40.00 Butyl rubber reclaim (same as in Example 1) 109.00

Fast-extruding furnace black 10.00 Semi-reinforcing furnace black 15.00 Zinc oxide 3.00 Stearic acid 1.00 Benzothiazyl disulfide 0.35 Sulfur 0.75

The foregoing formulation was mixed, shaped into inner tubes, and cured 5 minutes at 320 F. The resulting inner tubes (1I) were tested for air retention properties in tube tire assemblies along with regular production allvirgin Butyl inner tubes (I), and-all natural rubber inner tubes (111). The natural rubber stock which was used had air holding properties considerably superior to an allvirgin natural rubber stock because of a substantial content of natural rubber reclaim. The results of a 30 day air retention test are given in the following table. The figures are inflation pressures in pounds per square inch.

Days Test l o 5 12 i9 2s 30 Tuba I. Regular Production All Virgin Butyl Tube II. Tube Made from 60 Pts.

Butyl Reclaim Hydrocarbon and 40 Pts. Natural Ru ber.; III. Tube Made from All- Natural Rubber (including Natural Reclaim) These figures are plotted in Fig. 2 of the drawing. The great superiority of the inner tube made in accordance with the present invention over an all-natural rubber inner tube is clearly evident. It will be seen that the inner tube of the present invention was nearly as good in air retention as a regular production all-virgin Butyl tube.

Example 3 Liners for tubeless tires were made in the manner described above, from a 40 GR-S-60 Butyl reclaim stock The resulting tubeless tires were very satisfactory in all respects, particularly in air retention properties.

Example 4 Tubeless tires were constructed with liners made of a 60 Butyl reclaim-40 natural rubber reclaim stock having the following formulation:

Parts Natural rubberl reclaim l 2 68.00 Butyl rubberreclaim (same asin Example 1) 109.00

1A neutral blacky natural rubber tube reclaim analyzing as follows:

Sp. gr. 1.20

Extract percent 9 Ash do 20 Carbon black do 10 Rubber hydrocarbon do 58 v Tensile' i Y Y Y n B,i 1250 Elongation` at break percent.. 600,

2 40 parts hydrocarbon.

. 1 'Y 'Parts Fast-extruding furnace black 10.00 Semi-reinforcing furnace black 15.00 Zinc oxide 3.00 Stearic acid 1.00 Benzothiazyl disullide 0.35 Sulfur 2.00

Ordinary mixing and compounding techniques were used. The mode of forming the liners was that described above. The resulting liners were very satisfactory in all respects including air retention.

Example 4 clearly demonstrates the feasibility of completely replacing virgin natural rubber with reclaimed natural rubber.

Example 5 Tubeless tires were constructed with liners made of a 35 Butyl reclaim-65 natural rubber stock having the following formulation:

Parts #l smoked sheet 65.00 Butyl rubber reclaim (containing 55% rubber hydrocarbon) 63.63 lndopol H300 1 10.00 Philblack O (high abrasion furnace black) 50.00 Zinc oxide 5.00 Stearic acid 1.40 Monex (tetramethyl thiuram monosullide) 0.35 Sulfur 0.65

1A non-migratory plasticizer consisting of polybutenes of relatively low molecular weight and having the following properties Mean molecular weight Sp. gr. 60/60 F Flash point (Tag), F ASTM pour point, F Viscosity, S. E. sec. vat 210 F 3 Refractive index Iodine No Ordinary mixing and compounding techniques were used. The mode of forming the liners was that described above.

Samples of the liner stock of this example were cured at 350 F. and physical properties of the vulcanizates were determined. Other samples were cured while in contact with an uncured conventional natural rubber stock of the type used for coating tire cords after which the adhesion of the liner stock to the cord coating stock was determined. The data were as follows:

1 ASTM D-813-44T, 0.50 inch puncture hole growth considered failure.

The air permeability characteristics of samples of vulcanized liner stocks of Example 5 were determined. These vulcanizates exhibited an air'retenton equal to about three times that of a conventional vulcanized natural rubber inner tube stock.

A very important advantage of liners for tubeless tiree made in accordance with our invention is that they present no problem of adhesion to the ordinary rubber-coated innermost ply of the tire carcass. The adhesion of liners made in accordance with our invention to such rubbercoated plies is remarkably good, so good in fact that if the liner is pulled away from the tire carcass it frequently strips the rubber from the innermost fabric ply of the tire leaving exposed cord. This feature of our invention is highly advantageous because it provides a simple solution to the problem of adhesion of liners in tubeless tires to the interior of the tire, While making possible air retention properties closely approaching those of all-virgin Butyl rubber liners. In U. S. patent to Antonson 2,587,428 the problem of adhesion of an all-Butyl liner was solved by rubberizing only the outer side of the innermost ply of cord, leaving the inner side thereof uncoated so that during vulcanization the Butyl liner adhered directly to the uncoated innermost fabric ply. By the practice of our invention resort to such means for obtaining the necessary bond between the liner and ther 'tire carcass is obviated. In practicing our invention we use the ordinary tire carcass construction comprising a plurality of layers of tire cord all of which have been rubberized on both sides with natural rubber or GR-S or a mixture thereof, and adhesion of our liner to such rubberized fabric presents no problem whatever, apparently because of the fact that the rubber mixture used in our invention is completely compatible with natural rubber or GRS or mixtures thereof, whereas Butyl rubber is incompatible with natural rubber or GR-S.

Proportions of Butyl rubber reclaim hydrocarbon less than 30% are not satisfactory because of inadequate air retention properties. Proportions above 70% of Butyl rubber reclaim hydrocarbon based on total rubber content are not satisfactory because the physical properties are adversely impaired at such levels.

The term Butyl rubber is used herein in its ordinary sense to denote a sulfur-vulcanizable copolymer of a major proportion of isobutylene and a minor proportion of a multi-oleiinic unsaturate having from 4 to 14 carbon atoms per molecule, the multi-olefnic unsaturate usually being an aliphatic conjugated diolen hydrocarbon having from 4 to 6 carbon atoms per molecule, typically isoprene or butadiene, the proportions of combined monomers in the copolymer usually ranging from to 99.5% of isobutylene and correspondingly from l0 to 0.5% of the multi-oleinic unsaturate.

The term Butyl rubber reclaim is used herein in its ordinary sense to denote a material which, as is wellknown in the rubber art, is made by treating vulcanized Butyl rubber in such a way as to cause it to be devulcanized and attain a sufficiently plastic state to enable its re-use in making vulcanized rubber articles. As is wellknown, Butyl rubber reclaim is commonly made by heating ground Butyl rubber vulcanizate with water or steam in the presence of a reclaiming oil until it is softened and rendered suiciently plastic to be re-used like virgin rubber, after which it is sheeted out ready for sale. An example of such a process is shown in Randall U. S. Patent 2,545,828. Butyl rubber reclaim is a standard article of commerce and the method of making it is wellknown and constitutes no part of the present invention.

The term Butyl rubber reclaim hydrocarbon as used herein denotes the rubber hydrocarbon furnished by the Butyl rubber reclaim, and does not include any hydrocarbon oil or other non-rubber hydrocarbon component of the reclaim.

The terms natural rubber, GR-S, and butadienestyrene rubbery copolymer as used herein and in the appended claims include either virgin or reclaimed materials or mixtures of virgin and reclaimed materials, unless otherwise indicated by the context.

From the foregoing description, many advantages of the prtent intiem@ will be readily apparent to'those skilled in thel The principal advantage is that we provide an air retaining velement having air retention properties closely approaching those of the best all-Butyl rubber air retaining element thus far available. At the same time however, the air retaining element of our invention is not subject to the deficiencies of all-Butyl rubbei' air retaining elements. Perhaps the most important advantage of Your invention is that in the case of a tubeless tire we obtain remarkable adhesion of the liner to the rubberized tire carcass. As mentioned above, the adhesion of liners of our invention to the rubberized interior of the tirecarcass is extraordinary. ln this way, asexplained` above, we obviate the serious problem of adhesion of allButyl rubber liners to the inside of the tilt` carcass. Thereby we greatly simplify the mannfacture of tubeless tires and at the same time we obtain the great advantages yof air Iretention properties almost as good 8S. an all-Butyl rubber liner. Another very important advantageis that the stocks used in our invention handle in the'manner resembling ordinary natural rubber or GR-S stocks. Numerous other advantages will be apparent to those skilled in the art.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. A vulcanized tubeless pneumatic rubber tire comprising a multi-ply rubberized fabric carcass with surrounding side-wall and tread portions and having an interior air retaining liner secured directly to its innermost ply by vulcanization in situ, said liner being formed of a continuous body of a vulcanized mixture comprising a reclaim of a rubbery copolymer of a major proportion of isobutyleneY and a minor proportion of an aliphatic conjugated diolen hydrocarbon having from 4 to 6 carbon atoms per molcule and an elastomer selected from the group consisting of natural rubber and butadienestyrene rubbery copolymer in relative proportions of from 55 to 70 percent of rubber hydrocarbon furnished by said reclaim and correspondingly from 45 to 30% of said selected elastomer, said percentages being based on the sum ofthe 1eights of rubber hydrocarbon furnished by said reclaim and said selected elastomer, said reclaim having been made` by heating a vulcanized rubbery copolymer ofy a major proportion of isobutylene and a minor proportion of an aliphatic conjugated diolen hydrocarbon having from 4 to 6 carbon atoms per molecule in the presence of a reclaiming oil until said copolymer is suiciently plastic to enable it to be sheeted` out and re-used like virgin rubber in making vulcanized rubber articles.

2. Aftirc asfrecited in claimV 1 wherein said mixture contains from to 60 parts of carbon black per 100 parts, of. rubber hydrocarbon furnished by said reclaim and said selected elastomer@ V3. A vulcanized tubeless pneumatic rubber tire comprisinga carcassformed with plies of fabric coated with rubber selected from the group consisting of natural rubber andbutadiene-styrene rubbery copolymer, said carcass havingfsurrounding side-wall and tread portions, the innermost ply of fabric being coated on its inside face with rubber selected from said group, and an interior air retaining liner integrally secured to and coalesced` with the inner rubber coating on said innermost ply by vulcanization insitu, said liner being formed of a continuousrb'ody of a vulcanized mixture comprising a reclai'r'nrofi a rubbery copolymer of a major proportion of is'obutylcneand a minor proportion ofan aliphatic conjugated diolein hydrocarbon having from'4to 6 carbon atins' per 'molecule and an elastomer selectedfrom the group consisting of natural rubber and butadiene-styrene rubbery copolymer in relative proportions of from 55 to 70% of rubber hydrocarbon furnished by said reclaim andV correspondingly from to 30% of said selected elastomer, said percentages being based on the sum of the weights of rubber hydrocarbon furnished by said reclaim and said selected elastomer, said reclaim having been madeA by heating a vulcanized rubbery copolymer of a major proportion of isobutylene and a minor proportion Vof an aliphatic conjugated diolefin hydrocarbon having from 4 to 6 carbon atoms per molecule in the presence of a reclaiming oil until said copolymer is sufficiently plastic to enable it to be sheeted out and re-used like virgin rubber in making vulcanized rubber articles.

4. A vulcanized tubeless pneumatic rubber tire comprising a carcass 'formed with plies of fabric coated with rubber selected from the group consisting of natural rubber and butadiene-styrene rubbery copolymer, said carcass having surrounding side-wall and tread portions, the innermost ply of fabric being coated on its inside face with rubber selected from said group, and an interior air retaining liner integrally secured to and coalesced with the inner rubber coating on said innermost ply by vulcanization in situ, said liner being formed of a continuous body of a vulcanized mixture comprising a reclaim of a rubbery copolymer of a major proportion of isobutylene and a minor proportion of an aliphatic conjugated diolefin hydrocarbon having from 4 to 6 carbon atoms per molecule and natural rubber in relative proportions of from to 70% of rubber hydrocarbon furnished by said'reclaim and correspondingly from 45 to 30% of natural rubber, said percentages being based on the. sum of the weights of rubber hydrocarbon furnished by said reclaim and natural rubber, said reclaim having been made by heating a vulcanized rubbery copolymer of a major proportion of isobutylene and a minor proportion of an aliphatic conjugated diolen hydrocarbon having from 4 to 6 carbon atoms per molecule in the presence of a reclaiming oil` until said copolymer is sufiicicntly plastic to enable it to be sheeted out and re-used like virgin rubber in making vulcanized rubber articles.

References Cited in the file of this patent UNITED STATES PATENTS 2,332,194 Beckley Oct. 19, 1943 2,418,250 Drake Apr. 1, 1947 2,467,322 Lightbown et al. Apr. 12, 1949 2,541,550 Sarbach et al Feb. 13, 1951 2,545,828 Randall Mar. 20, 1951 2,557,642 Dudley June 19, 1951 2,575,249 Connell et al. Nov. 13, 1951 2,578,001 Cubberley etal. Dec. 11, 1951 2,583,387 Morrissey et al. Jan. 22, 1952 2,587,470 Herzegh Feb. 26, 1952 2,592,724 ONeil Apr. 15, 1952 2,635,975 Peters Apr. 21, 1953 FOREIGN PATENTS 512,948 Belgium Aug. 14, 1952 1,020,822 France Nov. 26, 1952 (Corresponding U. S. Sarbach 2,676,636, Apr. 27, 1954) OTHER REFERENCES Butex for Light and Ozone Resistance, Midwest Rubber Reclaiming Co.,4Report #12, lune 1, 1949. Modern Rubber Chemistry (Barron); published by D. Van Nostrand Co. (1948), pages 281-290. 

